Radiation detecting apparatus, scintillator panel, radiation detecting system, and method for producing scintillator layer

ABSTRACT

A radiation detecting apparatus includes: a sensor panel that has a substrate, and has a plurality of pixels each of which has a photoelectric conversion element for converting light into an electric signal, arranged on the substrate; and a scintillator layer arranged on a reverse side of the pixels with respect to the substrate, wherein the scintillator layer contains an activator added in a main ingredient, and has a higher concentration of the activator in a peripheral area than in a center area, in a surface direction of the scintillator layer.

RELATED APPLICATIONS

This application is a divisional of application Ser. No. 11/680,746,filed Mar. 1, 2007, claims benefit under 35 U.S.C. §120 of the filingdate of that application, and claims benefit under 35 U.S.C. §119 ofJapanese Patent Application No. 2006-056473, filed Mar. 2, 2006; theentire contents of each of the two mentioned prior applications arehereby incorporated by reference herein in their entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a radiation detecting apparatus, ascintillator panel, a radiation detecting system, and a method forforming a scintillator layer by deposition; and particularly relates tothe scintillator panel, the radiation detecting apparatus, theradioactive rays detection system, which are used in radiographing usedin medical diagnosis equipment and non-destructive inspection equipment,and the method for forming a scintillator layer by deposition. In thepresent specification, “radiation” shall include corpuscular rays suchas X-rays, gamma-rays, and alpha-particles and beta-particles. Inaddition, the “scintillator” shall be a device that converts incidentradiation such as X-rays and gamma-rays to light having a wavelengthrange that can be sensed by a photoelectric conversion element.

2. Description of the Related Art

A radiation detecting apparatus conventionally used in generalradiographing uses a radio-sensitized paper having a scintillator layerwhich converts X-rays into light, and a radiation film having aphotosensitive layer.

However, a digital radiation detecting apparatus has been recentlydeveloped which has a scintillator layer and a two-dimensionalphotodetector including photoelectric conversion elements. The digitalradiation detecting apparatus facilitates image processing because theobtained data is digital and the data can be shared among multiplepersons, when the data is taken into a networked computer system. Inaddition, if the image digital data is saved in a magneto-optical diskor the like, the digital radiation detecting apparatus can remarkablyreduce the storage space required, compared to the case of saving imagedata in a film, and has an advantage of facilitating a search for pastimages. In addition, the digital radiation detecting apparatus canreduce the dosage of exposure to radiation for the patient, because adigital radiation detecting apparatus having characteristics of highsensitivity and high sharpness has been proposed along with the progressof the apparatus.

For instance, International Publication Number WO 98/036290 discloses adigital radiation detecting apparatus that has a scintillator layerwhich is produced with a vacuum deposition technique and includescrystals of cesium iodide (hereafter referred to as CsI) grown into acolumnar shape, connected with a photodetector directly or through aprotection film. A thus configured digital radiation detecting apparatuscan be made with improved sensitivity and sharpness in comparison withthat provided with a scintillator layer having conventionalscintillators made of granular crystals assembled together.

In addition, International Publication Number WO 99/066350 discloses adigital radiation detecting apparatus having a configuration ofadhesively bonding a CsI surface of a scintillator prepared, forinstance, by vapor-depositing CsI on a base plate, to a photodetector(which is not shown in the drawings).

A columnar crystal of CsI or the like, which forms a scintillator layer,has properties of absorbing external moisture and deliquescing. Ascintillator layer having absorbed moisture deteriorates in its lightemission properties and sharpness. For this reason, the above-describedconventional radiation detecting apparatus or scintillator panel has amoisture proof protective film for preventing the entry of externalmoisture.

In addition, a radiation detecting apparatus disclosed in U.S. Pat. No.4,820,926 has an outermost layer containing only the activator of Tlformed on a light emission material layer.

However, it has been demanded to further improve a moisture-proofeffect. Particularly, radiation detecting apparatus for use in a hostileenvironment like a high-temperature and high-humidity environment hasbeen required to have an improved moisture-proof effect.

SUMMARY OF THE INVENTION

Accordingly, an object of the present invention is to provide aradiation detecting apparatus and a scintillator panel which have ahigher moisture-proof effect than ever before, and a method forproducing a scintillator layer having a sufficient moisture prooffunction.

A radiation detecting apparatus according to the present invention has:a sensor panel that has a substrate, and has a plurality of pixels eachof which has a photoelectric conversion element for converting lightinto an electric signal, arranged on the substrate; and a scintillatorlayer arranged over the pixels, wherein the scintillator layer containsan activator and a main ingredient, and has a higher concentration ofthe activator in a peripheral area than in a center area, in a surfacedirection of the scintillator layer.

In addition, a scintillator panel according to the present inventionhas: a substrate; and a scintillator layer arranged on the substrate,wherein the scintillator layer contains an activator added in a mainingredient and has a higher concentration of the activator in aperipheral area than in a center area, in a surface direction of thescintillator layer.

A method for producing a scintillator layer according to the presentinvention includes: arranging a vapor deposition boat for a mainingredient of the scintillator layer and a vapor deposition boat for anactivator in a vacuum chamber so as to face to a substrate on which thescintillator layer is to be deposited; arranging the vapor depositionboat for an activator at such a position as to face to a peripheral areaof the substrate; and conducting a vapor-depositing operation.

The present invention can provide a radiation detecting apparatus and ascintillator panel which inhibit the diffusion of moisture in aperipheral area of a scintillator layer, and have a sufficient moistureproof function; and a method for producing the scintillator layer havingthe sufficient moisture proof function.

Other features and advantages of the present invention will be apparentfrom the following description taken in conjunction with theaccompanying drawings, in which like reference characters designate thesame or similar parts throughout the figures thereof.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and constitute apart of the specification, illustrate embodiments of the invention and,together with the description, serve to explain the principles of theinvention.

FIG. 1 shows a sectional view of a radiation detecting apparatusaccording to the first embodiment of the present invention.

FIG. 2A is a plan view showing the Tl concentration in a scintillatorlayer of a radiation detecting apparatus according to the firstembodiment of the present invention.

FIG. 2B is a plan view showing the Tl concentration in a scintillatorlayer of a radiation detecting apparatus according to the firstembodiment of the present invention.

FIG. 3 is a characteristic view showing a relationship between Tlconcentration and a light emission coefficient.

FIG. 4 is a characteristic view showing a relationship between Tlconcentration and an MTF variation rate.

FIG. 5 is a schematic block diagram showing a vapor-deposition apparatusfor forming a scintillator layer by vapor deposition.

FIG. 6 is a characteristic view showing the dependency ofcharacteristics of Tl concentration and a light emission coefficient ontemperature.

FIG. 7 is a sectional view showing another configuration example of aradiation detecting apparatus according to the first embodiment of thepresent invention.

FIG. 8 shows a sectional view of a radiation detecting apparatusaccording to the second embodiment of the present invention.

FIG. 9 is a sectional view showing another configuration exampleaccording to the second embodiment of the present invention.

FIG. 10 is an equivalent circuit diagram showing a photoelectricconversion element array according to the first embodiment of thepresent invention.

FIG. 11 is a view showing an example in which a radiation detectingapparatus according to the present invention is applied as a radiationdetecting system.

FIG. 12 is a view showing a case of having heated a scintillator layerwith the use of a lamp heater.

DESCRIPTION OF THE EMBODIMENTS

In the next place, the best modes for carrying out the present inventionwill be described in detail with reference to the drawings.

First Embodiment

FIG. 1 shows a sectional view of a radiation detecting apparatusaccording to the first embodiment of the present invention. In FIG. 1,reference numeral 11 denotes a polyethylene terephthalate resin layerwhich is a support for an electromagnetic shield layer 12, and referencenumeral 12 denotes an aluminum layer which functions as anelectromagnetic shield body, and has a light reflection function and amoisture-proof function.

In FIG. 1, reference numeral 13 denotes a polyolefin-based hot-meltadhesive resin layer which is a thermoplastic resin layer having anadhesively bonding function and a moisture-proof function, referencenumeral 14 denotes a scintillator layer including columnar crystals,reference numeral 15 denotes an insulation layer, and reference numeral16 denotes a glass substrate. In addition, reference numeral 17 denotesa photoelectric conversion element array in which pixels including aphotosensor and a TFT using amorphous silicon are arrayed into atwo-dimensional form.

In FIG. 1, a scintillator layer 14 including columnar crystals is madefrom CsI as a main ingredient and Tl which is added as an activator. InFIG. 1, as shown in the scintillator layer 14, the variation of theconcentration of added Tl among the pixels is shown by a gray levelusing black and white. A black part in a peripheral area shows where Tlexists in high concentration, and as is clear from the figure, theconcentration of Tl gradually increases from a central part to theperipheral area. FIGS. 2A and 2B are two-dimensional views showing thedistribution of the Tl concentration when viewed from above. It isunderstood from the figures that the concentration of Tl generallyconcentrically and isotropically changes from the center of thescintillator layer 14 to the peripheral area on a glass substrate 16.The dashed line means that the Tl concentration is particularly high inthe peripheral area outside the line. FIG. 2A shows an example in whichthe Tl concentration is particularly high in four corners of the squareglass substrate, and FIG. 2B shows an example in which the Tlconcentration is high even in more inward parts. The Tl concentration inthe peripheral area does not need to be all uniform, but may be higherin a part of the peripheral area than in other parts, as needed. Forinstance, when a wire is drawn out from a photoelectric conversionelement array in a region 14 a, in a configuration in FIG. 2B,irregularities may be formed in an insulation layer 15 by the wire, andfacilitate moisture to enter the inner part through an interface betweenthe insulation layer 15 and the protection film 13. In such a case, themoisture durability of the scintillator layer 14 can be improved bymaking the Tl concentration in the region 14 a higher than that in theother peripheral areas. When it is a problem that moisture enters fromonly one part of the peripheral area, it is also acceptable to make theTl concentration higher only in that part, while making the Tlconcentration in all other parts equal to that in the central part.

It is considered that the moisture enters into the scintillator layer 14from the perimeter of the scintillator layer 14. In other words, it isconsidered that the moisture enters from an interface between the hotmelt adhesive resin layer 13 that serves as the moisture proofprotective film and a member (insulation layer) which directly contactswith the hot melt adhesive resin layer 13, gradually invades the innerpart, and diffuses toward the central part from a circumferential part(peripheral area) of the scintillator layer 14. In the presentembodiment, the scintillator layer 14 can prevent its peripheral areafrom deliquescing even when the moisture has invaded into thescintillator layer 14, and further inhibit moisture from diffusing intothe center area, by making the Tl concentration in the peripheral areahigher than that in the center area.

In the next place, a method for adding Tl will be described. It has beenelucidated from an experiment that a Tl concentration for making thescintillator layer 14 emit more light can be in a range shown by thefollowing expression, due to properties of CsI, when the concentrationof CsI containing Tl is determined as 100 [mol %]:

CsI(Tl):Tl=100:0.5 to 2.0[mol %]

FIG. 3 is a graph showing a relationship between Tl concentration and aquantity of light emission (light emission coefficient). The lightemission coefficient in FIG. 3 shows a ratio of a quantity of lightemission to the maximum quantity of light emission when the maximumquantity is determined as 1. As is shown in FIG. 3, the quantity oflight emission becomes maxim when the Tl concentration is about 1 to 1.5[mol %]. However, the Tl concentration can not be determined only fromthe quantity of light emission, because it is known that the sharpnessof the obtained image decreases with the increase of the Tlconcentration.

It is also elucidated from an experiment that the Tl concentration forgiving the scintillator layer 14 sufficient moisture-proof effects,namely, for effectively inhibiting moisture from diffusing can be insuch a range as to satisfy the following expression:

CsI(Tl):Tl=100:1.0[mol %] or more

FIG. 4 shows a relationship between Tl concentration and a variationrate of MTF (Modulation Transfer Function). In the experiment, thevariation rate of the MTF was determined by measuring the MTFs of asample before and after having been left in an environment with humidityof 50% at 25° C. for 24 hours. As is shown in FIG. 4, the variation rateof the MTF decreases along with the increase of the Tl concentration.When the Tl concentration is 0.7 [mol %] or higher, the variation rateis little affected by deliquescence, when the Tl concentration is 1.0[mol %] or higher, the deliquescence does not substantially cause anyproblem, and furthermore, when the Tl concentration exceeds 1.5 [mol %],the Tl concentration should show a sufficient protective effect even ina more severe environment. The reason why the MTF was adopted as anindex of the moisture-proof effect will now be described. When acolumnar crystal of CsI (Tl) absorbs moisture and deliquesces, an areaof the surface from which the columnar crystal emits light increases, oradjacent crystals adhere to each other, and consequently the crystalsemit light from almost one surface; in other words, lights emitted fromthe adjacent crystals are superposed. For this reason, as the columnarcrystals deliquescence over a wider range, the columnar crystals in thewider range cohere with each other, and their output light beams aresuperimposed on each other.

Then, an image including signals detected by a sensor becomes blurred,because the sensor detects many superposed light beams (information). Inother words, the MTF, which is the sharpness of the image, is decreased.The MTF is an index of the sharpness.

The MTF is measured by: firstly arranging a lead plate (or a lead platehaving an aperture of slit shape) for intercepting X-rays on an incidentside of the X-rays; irradiating a sensor with X-rays; determining anoutput of a sensor in a part intercepted by the lead plate as zero andan output of the sensor in a part not intercepted by the lead plate as1; measuring the output of the sensor in the end of the lead plate;Fourier-transforming the output in order to know how the output variesin the vicinity of the end; and numerically expressing a degree ofblurring in every spatial frequency. When the MTF is 0.5 at 21 p/mm forinstance, the value means that when two pairs of information of 1 and 0exist in one millimeter, the information changes from 1 to 0.5. In otherwords, it means that the information is blurred. The smaller the valueof the MTF, the more difficult the judgment for the difference between 1and 0 becomes.

As was described above, the Tl concentration in a peripheral area of ascintillator layer can be set at 1.0 [mol %] or higher, and further canbe set at a concentration higher than 1.5 [mol %]. On the other hand,the Tl concentration in the inner part than the peripheral area of thescintillator layer is 0.5 [mol %] or more but 1.5 [mol %] or less, inconsideration of a balance between the quantity of light emission andsharpness.

A practical method for forming a scintillator layer with a vapordeposition technique will be now described with reference to FIG. 5.

FIG. 5 shows a vapor deposition apparatus for vapor-depositing CsI (Tl)for forming a scintillator layer. In FIG. 5, reference numeral 16denotes a glass substrate on which a photoelectric conversion elementarray 17 is formed and the scintillator layer will be formed with avapor deposition technique, reference numeral 50 denotes a vacuum tank(vacuum chamber) in the vapor deposition apparatus, reference numeral 51denotes an evaporation boat on which TlI is placed, and referencenumeral 52 denotes an evaporation boat on which CsI is placed.

An evaporation boat 51 is arranged so as to face toward a peripheralarea of a glass substrate 16.

A scintillator layer having activators distributed in its planedirection by a vapor deposition method is formed, for instance, by:arranging a glass substrate 16 to be a base on a substrate holder asshown in FIG. 5 so that a surface to be vapor-deposited faces downward;arranging, for instance, many boats 52 for evaporating CsI and a boat 51for evaporating TlI on a heat source for vapor deposition at positionsshown in FIG. 5; evacuating a vacuum tank (vacuum chamber) 50 of a vapordeposition apparatus; and heating each boat by using the vapordeposition source while rotating the substrate holder around its center.Then, the vapor of CsI flies out from many boats of CsI, and deposits onthe surface to be vapor-deposited (shown by an arrow of a continuousline). On the other hand, Tl which is an activator deposits in highamounts in the peripheral area of the substrate holder, and deposits inlow amounts in the central part to form distribution, because Tl issupplied from one vapor deposition source and the vapor depositionsource is placed at a position apart from the rotation axis of thesubstrate holder.

The thus obtained scintillator is subjected to activating an activatorby heating the scintillator at an annealing temperature of 200° C. to400° C. for 0.5 to 5 hours, and then is used for producing a radiationdetecting apparatus. The annealing temperature must be set at such atemperature as not to affect photoelectric transfer characteristics of aphotoelectric conversion element formed on a glass substrate.

In the present embodiment, as described above, the Tl concentration canbe set at 1.5 [mol %] or higher in a peripheral area of a scintillatorlayer, and at 0.5 to 1.5 [mol %] in an inner portion than the peripheralarea, in consideration of a balance between the quantity of lightemission and sharpness. Then, there may be cases where the quantity oflight emission in the center area is larger than that in the peripheralarea, or the quantity of light emission in the peripheral area is largerthan that in the center area.

In other words, when the concentration of an activator is distributed ina scintillator layer, a quantity of light emission is distributed on thesurface of the scintillator layer. When it becomes a problem that thequantity of light emission varies from one portion to another, thisvariability of the quantity of light emission can be reduced, byannealing the scintillator layer in response to light emission quantitydistribution while making use of a phenomenon that the quantity of lightemission varies depending on an annealing temperature.

FIG. 6 is a view showing a dependency of the quantity of light emissionon an annealing temperature. In FIG. 6, the annealing temperature B isset at about 20% higher than the annealing temperature A. Then, it isclear that a scintillator layer annealed at a higher temperature is moreactivated by an activator and emits more light. However, after thescintillator layer is sufficiently activated, the quantity of lightemission does not increase any more, so that there is naturally an upperlimit in the annealing temperature. For instance, when the quantity oflight emission in a center area is lower than that in a peripheral area,the quantity of light emission in the central part can be increased bysetting the annealing temperature in the vicinity of the central part ata higher temperature, and the quantity of light emission in a plane of ascintillator layer can be made uniform by setting the annealingtemperature so as to be distributed in an annealing environment. Inorder to set the annealing temperature in the center area at a highertemperature, it is recommended to arrange a heat source such as aceramic heater, a lamp heater, and a combination of a metal plate and asheath heater at a position facing the center area of a substrate (whilenot arranging such a heat source facing the peripheral area), and toheat the scintillator layer. FIG. 12 is a view showing a case of havingheated a scintillator layer with the use of a lamp heater 18. Usablelamp heaters include a tungsten halogen lamp, a xenon arc lamp and agraphite heater.

Materials for a scintillator having a columnar structure include cesiumiodide and cesium bromide.

In addition, activators for these scintillators include sodium andthallium.

A support 11 in FIG. 1 can employ not only a polyethylene-based resinbut also a resin such as an acrylic resin, a phenol resin, a vinylchloride resin, a polypropylene resin, a polycarbonate resin and acellulosic resin, as its material.

In addition, an electromagnetic shield 12 can employ not only aluminumbut also a metal such as silver, a silver alloy, copper and gold, as itsmaterial.

Furthermore, a protection film 13 has only to be made from athermoplastic resin, but can be made from a hot melt resin of not only apolyolefin resin but also a polyester-based resin, a polyurethane-basedresin and an epoxy-based resin. The hot melt resin is defined as anadhesive resin made from a thermoplastic material which does not containany of water and a solvent, is solid at a room temperature, and iscompletely nonvolatile. (Thomas P. Flanagan, Adhesive Age, 9, No. 3, 28(1966)).

Thus, a hot melt resin contains no solvent and no water, and accordinglyhardly dissolves a scintillator made from an alkali halide. Ascintillator-protecting film using the hot melt resin hardly dissolvesthe scintillator even in a production process, because of being stackedon a scintillator layer without using a solvent.

A hot melt resin melts when the temperature rises and adheres to a bodyto be bonded, and when the resin temperature falls, the resin becomes asolid. The adhesive resin layer made of the hot melt resin is differentfrom a solvent-volatilizing and curing type of an adhesive resin layerwhich is formed by a method of dissolving a thermoplastic resin in asolvent and applying the liquid on the body. The hot melt resin isdifferent also from a chemical reaction type of an adhesive resin whichis represented by an epoxy resin and is formed by a chemical reaction.

Hot melt resin materials can be classified mainly into apolyolefin-based resin, a polyester-based resin and a polyamide-basedresin. It is important for the protection film 13 to have a highfunction as a moisture-proof film and transmit visible rays (350 nm to700 nm) emitted from a scintillator. Hot melt resins having a sufficientmoisture-proof function can include polyolefin resins and polyesterresins. Particularly, polyolefin resins can be employed because ofhaving a low coefficient of moisture absorption. Polyolefin resins arealso suitable because of having high optical transparency.

Accordingly, a polyolefin-based hot melt resin for a protective layer ofthe scintillator can be used.

The hot melt resin can contain at least one compound selected from thegroup consisting of an ethylene-acrylic acid copolymer (EAA), anethylene-acrylate copolymer (EMA), an ethylene-methacrylic acidcopolymer (EMAA), an ethylene-methacrylate copolymer (EMMA) and anionomer resin, as a main component.

Additives to be added to an adhesive include, for instance, a tackifierand a softener.

Tackifiers include: a natural resin such as rosin, polymerized rosin,hydrogenated rosin and a rosin ester; a modified product thereof; analiphatic compound; an alicyclic compound; an aromatic compound; apetroleum resin; a terpene resin; a terpene-phenolic resin; ahydrogenated terpene resin and a chroman resin. Softeners, for instance,include: process oil, paraffin oil, castor oil, polybutene andlow-molecular-weight polyisoprene.

A copolymer contained in an adhesive layer has a weight averagemolecular weight of about 5,000 to 1,000,000. An ethylene-acryliccopolymer (EAA) has a structure in which a carboxyl group is containedin a polyethylene structure at random as shown in the followingstructural formula (I):

—(CH₂—CH₂)n-(CH₂—CHCOOH)m-

(wherein m and n are positive integers).

In addition, an ethylene-acrylate copolymer is a copolymer of ethyleneand acrylate, as is shown in the following structural formula (II):

—(CH₂—CH₂)n-(CH₂—CHCOOR)m-

(wherein m and n are positive integers, and R represents CH₃, C₂H₅ orC₃H₇).

In addition, an ethylene-methacrylic copolymer has a structure in whicha carboxyl group is contained in a polyethylene structure at random asshown in the following structural formula (III):

—(CH₂—CH₂)n-(CH₂—CCH₃COOH)m-

(wherein m and n are positive integers).

Furthermore, an ethylene-methacrylate copolymer has such a structure asis shown in the following structural formula (IV):

—(CH₂—CH₂)n-(CH₂—CCH₃COOR)m-

(wherein m and n are positive integers, and R represents CH₃, C₂H₅ orC₃H₇).

A protection film 13 contains at least one copolymer among the abovedescribed five copolymers or may contain a mixture of two or more of thecopolymers. An adhesive layer in the present invention may contain themixture of the two or more different but similar copolymers, forinstance, the mixture of an ethylene-methyl methacrylate copolymer andan ethylene-ethyl methacrylate copolymer.

A melting-starting temperature, melt viscosity and adhesion strength ofa hot melt resin for a scintillator-protecting film can be controlled,by mainly appropriately changing the following three elements alone orin combination of two or more: (1) contents of vinyl acetate, acrylicacid, acrylate, methacrylic acid and methacrylic ester in the abovedescribed respective copolymers contained in a hot melt resin; (2) acontent of the above described copolymer in a hot melt resin; and (3) anadditive in a hot melt resin.

A hot melt resin can be used as a scintillator-protecting film in aradiation imaging element for a human body not to aggravate its functionas a scintillator-protecting layer, even when sterilizing alcohol hasbeen scattered thereon.

A hot melt resin which is insoluble or slightly soluble in ethyl alcoholcan contain an additive such as an adhesion-imparting material in thehot melt resin in an amount of 20% or less, and particularly in anamount of 10% or less.

In the next place, a photoelectric conversion element array havingpixels including a photo sensor and a TFT two-dimensionally formedthereon will be described with reference to an equivalent circuitdiagram in FIG. 10. In FIG. 10, a photoelectric conversion element 301,a transfer-switching element 302 and a resetting switch element 303 aretwo-dimensionally arranged. At first, a bias is given on one electrodeof a photoelectric conversion element 101 through a bias wiring 304. Inthis state, X-rays projected toward an object pass through the objectwhile being damped, and irradiate a scintillator arranged on aphotoelectric conversion element 301. Then, the scintillator convertsthe X-rays to light such as visible light. The light is incident on thephotoelectric conversion element 301 and is converted to electricalcharge. The electrical charge is transferred to a signal wire 306 bymaking a drive apparatus 310 apply a gate-driving pulse to a gate wire305 to control a transfer-switching element 302 into a conductive state,and is read to the outside by a read apparatus 309. Subsequently, aresetting switch element 303 is converted into the conductive state bymaking the drive apparatus 310 apply the gate-driving pulse to a gatewire 307. Meanwhile, a bias for resetting the photoelectric conversionelement is applied to a resetting wire 308, and a residual charge whichhas been generated in the photoelectric conversion element 301 but hasnot been all transferred is removed.

Picture signals for one image are obtained by repeating theabove-described operation, and an image is obtained by furtherrepeatedly acquiring the picture signals for another image. FIG. 10shows 3×3 pixels, but practically more pixels such as 2,000×2,000 pixelsare arranged on an insulation substrate to compose a radiation detectingapparatus. In addition, a resetting switch element is not necessarilyprovided.

A photoelectric conversion element array used in the present embodimenthas a TFT and a photoelectric conversion element formed on a glasssubstrate so as to be aligned on the same plane. However, aphotoelectric conversion element array can also be used which has aconfiguration having a switching element such as a TFT formed on theglass substrate, a medium of an insulation layer, and a photoelectricconversion element formed thereon. Even the photoelectric conversionelement array with such a configuration has two types. One is aconfiguration in which a photoelectric conversion layer (semiconductorlayer) of the photoelectric conversion element is not stacked on a TFTso that a defective region produced in the TFT can be repaired by usinga laser beam. The other is a configuration in which the photoelectricconversion layer (semiconductor layer) of the photoelectric conversionelement is stacked even on the TFT to increase an aperture ratio.

The present embodiment can impart a scintillator layer in itself amoisture-proof function by increasing Tl concentration in the perimeterof the scintillator layer for the purpose of further enhancing thereliability for a moisture-proof effect, though the moisture-proofeffect can be obtained only by a single moisture-proof protective layerof a hot melt resin.

Thereby, a radiation detecting apparatus having higher reliability at alow cost can be accomplished, because there is no need to add amechanism for protecting a scintillator layer, so that steps andmaterials can be reduced.

In the present embodiment, a thermoplastic resin layer is used as amoisture-proof protective layer for a scintillator layer, but this layeris not limited to the use of a thermoplastic resin. Any material can beused as long as it has a moisture-proof effect and an adhesive function.For instance, a sticky material is also acceptable.

In the above described example, the Tl concentration approximatelyconcentrically and isotropically changes from the center to a peripheralarea, as is shown in FIG. 1. The present embodiment can employ not onlysuch concentration distribution as is shown in FIG. 7, but also aconcentration distribution in which a region 21 a with a high TlIconcentration is arranged only in a peripheral end within a scintillatorlayer. FIG. 7 is a sectional view of a radiation detecting apparatus. InFIG. 7, only the black region 21 a in the peripheral end of thescintillator layer 21 has a high Tl concentration. In this case, it isacceptable that the Tl concentration is uniform within a concentriccircle and the Tl concentration is higher outside the concentric circle.In addition, the concentration distribution is not limited to aconcentric circle shape, but may be a frame shape in which theperipheral area has a frame shape and high Tl concentration, and theinner part inside the frame part has a uniform Tl concentration.

The scintillator layer having a uniform Tl concentration in a part otherthan the peripheral area can also show uniform characteristics such as aquantity of light emission and sharpness. In other words, an example asshown in FIG. 7 can have uniform characteristics in a part other thanthe peripheral end, while reliably imparting a moisture-proof effect toa scintillator in itself.

Second Embodiment

FIG. 8 shows a sectional view of a radiation detecting apparatusaccording to the second embodiment of the present invention. In thepresent embodiment, the radiation detecting apparatus is composed bylaminating a scintillator panel with a sensor panel through an adhesive.

The scintillator panel is produced by forming a scintillator layer on abase plate which allows X-rays to pass through itself as amorphouscarbon does, with a vapor-deposition technique. The used sensor panelhas an insulation layer 15 formed on a glass substrate 16 having aphotoelectric conversion element array 17 formed thereon, as is shown inFIG. 1. The radiation detecting apparatus is produced by bonding thesurface of the scintillator panel in a reverse side to the base plate,with the sensor panel having a photoelectric conversion element formedthereon, by using an adhesive.

In FIG. 8, reference numeral 31 denotes a base plate made from amorphouscarbon, reference numeral 32 denotes an insulation layer, referencenumeral 33 denotes an Al layer for reflecting light, reference numeral34 denotes an insulation layer, and reference numeral 35 denotes ascintillator layer made from CsI and TlI. In addition, reference numeral36 denotes a thermoplastic resin which is a moisture-proof protectivelayer, and reference numeral 37 denotes a polyethylene terephthalateresin layer which allows light to pass through it.

A concentration distribution of Tl and a method of adding Tl are omittedbecause of being similar to the case which was described in the firstembodiment with reference to FIGS. 1, 2A, 2B, 3, 4, 5 and 6.

It goes without saying that an effect equal to that in the firstembodiment is obtained in the present embodiment as well. In addition,the present embodiment can confirm the characteristics by using a singlescintillator panel alone. The radiation detecting apparatus according tothe present embodiment can be manufactured with an enhanced yield,because when the scintillator panel or the sensor panel has a defect, itcan be eliminated before being laminated.

FIG. 9 shows another example of a configuration according to the presentembodiment. The configuration example in FIG. 9 employs theconfiguration shown in FIG. 7 as a scintillator panel. Specifically, ascintillator layer 41 has a higher Tl concentration only in a peripheralend 41 a. It goes without saying that the configuration example alsoshows the same effect as in the case of the first embodiment describedwith reference to FIG. 7.

Third Embodiment

FIG. 11 is a view showing an example in which a radiation detectingapparatus according to the present invention is applied as a radiationdetecting system. The radiation detecting apparatus is the radiationdetecting apparatus in the above described respective embodiments.

As shown in FIG. 11, X-rays 6060 generated in an X-ray tube 6050 of aradiation source pass through the thorax 6062 of a patient or subject6061, and is incident on a radiation detecting apparatus 6040 for takinga radiation image. The incident X-rays include information about theinterior of the body of the patient 6061. A scintillator in theradiation detecting apparatus 6040 emits light in response to incidentX-rays, and the light is photoelectrically converted to electricinformation. The information is converted into digital signals. Thedigital signals are image-processed into an image by an image processor6070 of a signal processing unit. Then, the image can be observedthrough a display 6080 of a display unit in a control room.

The information can be also transferred to a remote place through atransfer unit such as a telephone line 6090, and can be displayed on adisplay 6081 of the display unit arranged in a doctor's office locatedelsewhere, or can be saved in a recording unit such as an optical disk.Thereby, a doctor at a remote place can examine the patient. Theinformation can be recorded in a film 6110 of a recording medium byusing a film processor 6100 of a recording unit.

As many apparently widely different embodiments of the present inventioncan be made without departing from the spirit and scope thereof, it isto be understood that the invention is not limited to the specificembodiments thereof except as defined in the claims.

While the present invention has been described with reference toexemplary embodiments, it is to be understood that the invention is notlimited to the disclosed exemplary embodiments. The scope of thefollowing claims is to be accorded the broadest interpretation so as toencompass all such modifications and equivalent structures andfunctions.

1. A manufacturing method of a radiation detecting apparatus includingsteps of: placing a substrate having a photoelectric conversion elementat a substrate holder; and forming a scintillator layer, on thesubstrate, from a main ingredient evaporated from a main ingredientevaporation boat placed at a first side of the substrate, and from anactivator evaporated from an activator evaporation boat placed, at thefirst side of the substrate, at a position apart from a center axis ofthe substrate, such that the scintillator layer contains the activatorin a higher concentration in a peripheral area rather than theconcentration in a center area.
 2. The manufacturing method of aradiation detecting apparatus according to claim 1, further comprising astep of arranging a metal layer covering the scintillator layer.
 3. Themanufacturing method of a radiation detecting apparatus according toclaim 1, wherein the concentration of the activator in the peripheralarea of the scintillator layer is 1.0 mol % or more with respect to theconcentration of main ingredient, and the concentration of the activatorin a central part of the scintillator layer is 0.5 mol % or more but 1.5mol % or less with respect to the concentration of main ingredient. 4.The manufacturing method of a radiation detecting apparatus according toclaim 1, wherein the scintillator layer is made of a columnar crystalstructure.
 5. The manufacturing method of a radiation detectingapparatus according to claim 1, further comprising a step of annealingthe scintillator layer such that an annealing temperature of the centerarea is higher than an annealing temperature of the peripheral area. 6.The manufacturing method of a scintillator panel according to claim 2,further comprising a step of arranging a light transmitting resin layercovering the scintillator layer.
 7. A manufacturing method of ascintillator panel including steps of: placing a base plate at a holder;and forming a scintillator layer, on the substrate, from a mainingredient evaporated from a main ingredient evaporation boat placed ata first side of the base plate, and from and an activator evaporatedfrom an activator evaporation boat placed, at the first side of the baseplate, at a position apart from a center axis of the base plate, suchthat the scintillator layer contains the activator in a higherconcentration in a peripheral area rather than the concentration in acenter area.
 8. The manufacturing method of a scintillator panelaccording to claim 7, wherein the concentration of the activator in theperipheral area of the scintillator layer is 1.0 mol % or more withrespect to the concentration of main ingredient, and the concentrationof the activator in a central part of the scintillator layer is 0.5 mol% or more but 1.5 mol % or less with respect to the concentration ofmain ingredient.
 9. The manufacturing method of a scintillator panelaccording to claim 7, wherein the scintillator layer is made of acolumnar crystal structure.
 10. The manufacturing method of ascintillator panel according to claim 7, further comprising a step ofannealing the scintillator layer such that an annealing temperature ofthe center area is higher than an annealing temperature of theperipheral area.
 11. A manufacturing method of a radiation detectingapparatus including: a step of preparing a substrate having aphotoelectric conversion element; a step of preparing a scintillatorpanel according to claim 7; and a step of bonding together the substrateand the scintillator panel.